Limited Occurrence of Denitrification in Four Shallow Aquifers in Agricultural Areas of the United States

The ability of natural attenuation to mitigate agricultural nitrate contamination in recharging aquifers was investigated in four important agricultural settings in the United States. The study used laboratory analyses, field measurements, and flow and transport modeling for monitoring well transects (0.5 to 2.5 km in length) in the San Joaquin watershed, California, the Elkhorn watershed, Nebraska, the Yakima watershed, Washington, and the Chester watershed, Maryland. Ground water analyses included major ion chemistry, dissolved gases, nitrogen and oxygen stable isotopes, and estimates of recharge date. Sediment analyses included potential electron donors and stable nitrogen and carbon isotopes. Within each site and among aquifer-based medians, dissolved oxygen decreases with ground water age, and excess N2 from denitrification increases with age. Stable isotopes and excess N2 imply minimal denitrifying activity at the Maryland and Washington sites, partial denitrification at the California site, and total denitrification across portions of the Nebraska site. At all sites, recharging electron donor concentrations are not sufficient to account for the losses of dissolved oxygen and nitrate, implying that relict, solid phase electron donors drive redox reactions. Zero-order rates of denitrification range from 0 to 0.14 μmol N L−1d−1, comparable to observations of other studies using the same methods. Many values reported in the literature are, however, orders of magnitude higher, which is attributed to a combination of method limitations and bias for selection of sites with rapid denitrification. In the shallow aquifers below these agricultural fields, denitrification is limited in extent and will require residence times of decades or longer to mitigate modern nitrate contamination

The Vehicle, 1963, Vol. 5

Vol. 5 Table of Contents Milepostspage 3 Rhyme Conceived At DawnDaun Alan Leggpage 4 NightRoss Kokospage 4 UncrownedOra Blanche T. Kingpage 4 SunfishingL.J.G.page 5 The Man Who Went To New YorkEric Crookspage 7 The DreamPauline B. Smithpage 18 Open WindowsDavid Helmpage 19 SalvationChristine McCollpage 19 The Chess GamePierre Hooverpage 20 CataclysmRaymond Kapraunpage 20 A Microscopic ViewKenneth L. Vadovskypage 21 See How Love ComesLiz Puckettpage 21 A Can Of Beer For AndyKenneth L. Vadovskypage 22 A MonsterDixie Lee Motleypage 28 InconstancyJanice Brookspage 29 DreamerDaun Alan Leggpage 29 The Third WishGlenda Vursellpage 30 The MiracleJanice Brookspage 32 What Lives Where Love Once Dwelt?Vernell Vyvialpage 33 The Most Unforgettable Person I Have Ever KnownJames Flingpage 34 Winter ThoughtsPauline B. Smithpage 35 A Winter NightPeggy Lambertpage 35 The Silver WhaleL.J.G.page 36 RaindropsDixie Lee Motleypage 40 Conflict Of Soul IJean Konzelmanpage 40 JudyChristine McCollpage 41 Sadness No. 3 (Vergessen)Sherry Sue Frypage 41 Lost GoldLarry Pricepage 42 EchoesCharles Cooleypage 48 TruthDaun Alan Leggpage 48 SunsetCarol Bennettpage 48 Cover designTom Windsor Illustration for winning storyJoel E. Hendrickshttps://thekeep.eiu.edu/vehicle/1011/thumbnail.jp

The Vehicle, 1964, Vol. 6

Vol. 6 Table of Contents Milepostspage 2 John Fitzgerald Kennedy Memorial Pagepage 4 Sadness No. 4 (Sorgen)Sherry S. Frypage 5 Christian BurialRoger J. Barrypage 7 The World of BeautyDavid Helmpage 9 The Song of the LarksDon Kapraunpage 10 ContrastKeith Haierpage 13 PanoramaDaun Alan Leggpage 13 A Child\u27s View of DeathCherie Brondellpage 14 RegretLiz Puckettpage 16 Brutal WarMary H. Soukuppage 17 aloneLiz Puckettpage 18 MadgeLinda Galeypage 19 Moon WatchingJoel E. Hendrickspage 20 AnalysisLiz Puckettpage 21 UniverseRick Talleypage 21 Anyone Can Be A LuniticRick Towsonpage 22 I, Too, Have A Rendezvous with DeathElaine Lancepage 23 The ReturnRobert D. Thomaspage 24 NamesLarry Gatespage 25 Eternal MomentsDavid Helmpage 25 The Last DaysPauline B. Smithpage 26 BeliefRichard J. Wiesepage 27 StormPauline B. Smithpage 28 ExplosionLiz Puckettpage 29 Autumn EveJoel E. Hendrickspage 29 The Girl On the White PonyLarry Gatespage 31 HoffnungTerry Michael Salempage 33 Stone WallsDaun Alan Leggpage 34 AdorationGail M. Barenfangerpage 37 MirageRoy L. Carlsonpage 38 Nature and NonsenseRick Talleypage 39 A Step Through A Looking GlassMarilyn Henrypage 40 Thoughts of a Summer PastPauline B Smithpage 42 Indiana GrassLarry Gatespage 43 RedondillaRoberta Matthewspage 44 Summer LoveDaun Alan Leggpage 45 To Youth Reaching For MaturityDavid Helmpage 45 Thanksgiving DayJoel E. Hendrickspage 46 Sadness No. 6 (Schatten)Sherry S. Frypage 48https://thekeep.eiu.edu/vehicle/1012/thumbnail.jp

Transport and Fate of Nitrate at the Ground-Water/Surface-Water Interface

Although numerous studies of hyporheic exchange and denitrification have been conducted in pristine, high-gradient streams, few studies of this type have been conducted in nutrient-rich, low-gradient streams. This is a particularly important subject given the interest in nitrogen (N) inputs to the Gulf of Mexico and other eutrophic aquatic systems. A combination of hydrologic, mineralogical, chemical, dissolved gas, and isotopic data were used to determine the processes controlling transport and fate of 3− in streambeds at five sites across the USA. Water samples were collected from streambeds at depths ranging from 0.3 to 3 m at three to five points across the stream and in two to five separate transects. Residence times of water ranging from 0.28 to 34.7 d m-1 in the streambeds of N-rich watersheds played an important role in allowing denitrification to decrease 3− concentrations. Where potential electron donors were limited and residence times were short, denitrification was limited. Consequently, in spite of reducing conditions at some sites, 3− was transported into the stream. At two of the five study sites, 3− in surface water infiltrated the streambeds and concentrations decreased, supporting current models that NO3− would be retained in N-rich streams. At the other three study sites, hydrogeologic controls limited or prevented infiltration of surface water into the streambed, and ground-water discharge contributed to NO3− loads. Our results also show that in these low hydrologic-gradient systems, storm and other high-fl ow events can be important factors for increasing surface-water movement into streambeds

The Vehicle, 1964, Vol. 6

Vol. 6 Table of Contents Milepostspage 2 John Fitzgerald Kennedy Memorial Pagepage 4 Sadness No. 4 (Sorgen)Sherry S. Frypage 5 Christian BurialRoger J. Barrypage 7 The World of BeautyDavid Helmpage 9 The Song of the LarksDon Kapraunpage 10 ContrastKeith Haierpage 13 PanoramaDaun Alan Leggpage 13 A Child\u27s View of DeathCherie Brondellpage 14 RegretLiz Puckettpage 16 Brutal WarMary H. Soukuppage 17 aloneLiz Puckettpage 18 MadgeLinda Galeypage 19 Moon WatchingJoel E. Hendrickspage 20 AnalysisLiz Puckettpage 21 UniverseRick Talleypage 21 Anyone Can Be A LuniticRick Towsonpage 22 I, Too, Have A Rendezvous with DeathElaine Lancepage 23 The ReturnRobert D. Thomaspage 24 NamesLarry Gatespage 25 Eternal MomentsDavid Helmpage 25 The Last DaysPauline B. Smithpage 26 BeliefRichard J. Wiesepage 27 StormPauline B. Smithpage 28 ExplosionLiz Puckettpage 29 Autumn EveJoel E. Hendrickspage 29 The Girl On the White PonyLarry Gatespage 31 HoffnungTerry Michael Salempage 33 Stone WallsDaun Alan Leggpage 34 AdorationGail M. Barenfangerpage 37 MirageRoy L. Carlsonpage 38 Nature and NonsenseRick Talleypage 39 A Step Through A Looking GlassMarilyn Henrypage 40 Thoughts of a Summer PastPauline B Smithpage 42 Indiana GrassLarry Gatespage 43 RedondillaRoberta Matthewspage 44 Summer LoveDaun Alan Leggpage 45 To Youth Reaching For MaturityDavid Helmpage 45 Thanksgiving DayJoel E. Hendrickspage 46 Sadness No. 6 (Schatten)Sherry S. Frypage 48https://thekeep.eiu.edu/vehicle/1012/thumbnail.jp